In a rotary machine such as a compressor and a turbine, at least one of a stationary vane or a rotor blade may be configured as a variable blade that is revolvable about a pivot axis along the radial direction of a hub, to adjust the attack angle with respect to flow.
In a rotary machine provided with such a variable blade, if the variable blade is configured such that the hub-side end surface of the variable blade does not interfere with the blade-facing surface of the hub in the rotation range of the variable blade, clearance between the hub-side end surface of the variable blade and the blade-facing surface of the hub is likely to increase when the variable blade is revolved toward the close side (in a direction that the angle between the chord line of the variable blade and the axial direction of the hub increases). Furthermore, if the rotary machine is configured such that the tip-side end surface of the variable blade does not interfere with the blade-facing surface of the casing in the rotation range of the variable blade, clearance between the tip-side end surface of the variable blade and the blade-facing surface of the casing is likely to increase when the variable blade is revolved toward the open side (in a direction that the angle between the chord line of the variable blade and the axial direction of the hub decreases). As described above, if the clearance between the hub-side end surface of the variable blade and the blade-facing surface of the hub or the clearance between the tip-side end surface of the variable blade and the blade-facing surface of the casing increases, loss due to a leakage flow that passes through the clearance (hereinafter, referred to as clearance loss) increases, and the efficiency of the rotary machine may decrease.
Patent Document 1 discloses a rotary machine with a variable blade including a spherically-shaped hub-side end surface recessed outward in the radial direction of the hub and a hub including a blade-facing surface which has a spherically-shaped spherical region protruding outward in the radial direction of the hub, so that the clearance between the hub-side end surface of the variable blade and the blade-facing surface of the hub does not increase at rotation of the variable blade toward the closing side.
Patent Document 2 discloses a configuration in which a trench is formed on the inner surface of the casing that faces the tip-side end surface of the blade and the tip-side end surface of the blade protrudes into the groove, to suppress a decrease in the efficiency of the rotary machine device due to a leakage flow that passes through the clearance between the tip-side end surface of the blade and the blade-facing surface of the casing.